1. Field of the Invention
The present invention relates to methods and systems for performing medical procedures on anatomical structures of the body. Such medical procedures may involve, for example, attenuating transient pressure waves in anatomical structures of the body, for example, by implanting a compressible pressure-attenuating device in an anatomical structure of the body that is subjected to such pressure waves.
2. Description of the Related Art
Pressure waves are known to propagate through incompressible fluids in various anatomical structures of the body. These pressure waves may be caused by normally-occurring events within the body, such as a beating heart, breathing in the lungs, peristalsis actions in the GI tract, and movement of the muscles of the body. Alternatively, these pressure waves may be caused by sudden events, such as coughing, laughing, external trauma to the body, and movement of the body relative to gravity. As the elasticity of the surrounding tissues and organs, sometimes referred to as compliance, decreases, the propagation of these pressure waves increases. These pressure waves have many undesirable effects ranging from discomfort to stress on the organs and tissue to fluid leakage to renal failure to stroke to heart attack to blindness.
Urinary tract disorders, such as frequency, urgency, incontinence, and cystitis, are a widespread problem in the United States and throughout the world, affecting people of all ages, both physiologically and psychologically. Urine is primarily composed of water and is a virtually incompressible fluid in the typical pressure ranges that are present within the human bladder. The relationship between the maximum urethral pressure and the intravesical pressure for normal voiding of the bladder is well-defined. During normal voiding, relaxation of the urethra occurs before the detrusor muscle contracts to cause the intravesical pressure to exceed the urethral pressure.
Intravesical pressure spikes often result from volumetric tissue displacement in response to gravity, muscular activity or rapid acceleration. The lack of compliance of the bladder and the urine contained in the bladder with respect to events of high frequency, high intensity and short wavelength results in minimal fluidic pressure attenuation of the higher frequency pressure wave(s) and results in high intravesical pressures that are directly transmitted to the bladder neck and urethra, which may or may not cause detrusor contractions. Under these conditions, the urethra may act as a volumetric pressure relief mechanism, allowing a proportional volume of fluid to escape the bladder, thereby lowering the intravesical pressure to a tolerable level. The urethra has a maximum urethral pressure value, and when the intravesical pressure exceeds the maximum urethral pressure, fluid will escape the bladder. Under these conditions, nerve receptors in the bladder and/or bladder neck and/or trigone trigger a detrusor contraction that may lead to matriculation (frequency) or may subside without matriculation (urgency) or may lead to the intravesical pressure exceeding the maximum urethral pressure resulting in fluid escaping the bladder (stress incontinence).
For the vast majority of patients suffering from problems of urinary tract disorders, such as frequency, urgency, stress and urge incontinence and cystitis, the cause and/or contributor to bladder dysfunction is a reduction of overall dynamic bladder compliance, as opposed to a reduction of steady-state bladder compliance. These patients may often have bladders that are compliant in steady-state conditions but that become non-dynamically compliant when subjected to external pressure events having a short duration of, for example, less than 5 seconds or, in some cases, less than 0.5 seconds. Reduction in dynamic compliance of the bladder is often caused by aging, use, distention, childbirth and trauma. In addition, the anatomical structure of the bladder in relation to the diaphragm, stomach, and uterus (for women) causes external pressure to be exerted on the bladder during physical activities, such as talking, walking, laughing, sitting, moving, turning, and rolling over. For a patient suffering from stress incontinence due to lack of dynamic compliance in the bladder, when the intravesical pressure exceeds the maximum urethral pressure, leakage occurs.
In light of the foregoing, a number of attempts have been made to combat urinary tract disorders. One such attempt involves the use of an indwelling catheter connected to a collection bag with a clamping device on the catheter. Indwelling catheters, however, have a number of drawbacks. For instance, there is an infection risk associated with indwelling catheters, which provide a direct passage for bacteria or other microorganisms into the bladder. Thus, indwelling catheters can only be used for relatively short-term situations. In addition, indwelling catheters and associated collection bags are not cosmetically appealing to most patients.
An approach that has been taken to address urinary incontinence involves the use of prosthetic urethral valves. One known prosthetic urethral valve utilizes an inflatable cuff that is inserted around the outside of the urethra. Prosthetic urethral valves also have numerous disadvantages. One disadvantage of these valves is that they typically require surgery for installation, and some of these valves must be operated externally and, therefore, are dependent on manual intervention.
The use of intra-urethral valves to address urinary tract disorders is also known. Typical intra-urethral valves also generally require manual intervention. Another problem associated with typical intra-urethral valves is that the valves may be displaced into the bladder or expelled from the urethra. There is also an infection risk associated with many such valves since they often extend into the meatus and/or have portions of the device external to the urethra providing a passage for microorganisms into the bladder.
Electrical stimulation therapy, including rectal, intra-vaginal, and external varieties, has been used to tone the muscles and to stimulate nerves supporting the bladder and urethra. However, this type of therapy requires lengthy and numerous treatments, and any benefits derived from the therapy typically diminish when the treatments are stopped.
Current surgical incontinence procedures typically focus on the augmentation of urethral flow resistance. Such surgical interventions typically include bladder neck suspensions and bulk (collagen) injections. Although these procedures can be clinically effective with certain patients, problems include widely variable clinical outcomes, relatively high costs to perform, and potential complications related to surgery. Moreover, the effects of such surgical procedures may be short-lived.
Drug therapy also exists for a number of urinary tract conditions, including overactive bladder. These drugs include oral medications (systemic) and drugs delivered directly into the bladder. Unfortunately, these drugs typically suffer from side effects, lack of efficacy and high morbidity. In particular, oral medications typically do not provide immediate relief of symptoms and include side effects, such as dry mouth and constipation. Drugs delivered directly into the bladder often require continuous or intermittent catheterization for introduction of the therapeutic agents at the clinically appropriate time.
As can be appreciated, the treatment methods described above either focus on the augmentation of urethral flow resistance, the temporary stoppage or absorption of all urethral flow, or the relaxing of the detrusor muscles to minimize unwanted contractions. The disadvantages and limitations of these treatment methods are numerous and include: an excessively high level of patient interaction required to operate and/or to maintain the devices, especially for elderly patients and for physically or mentally challenged patients; limited clinical efficacy; restricted urine outflow; patient discomfort and side effects; urethral and bladder infections related to the devices used; and relatively great expense as compared to non-clinical solutions (diapers, pads, etc.).
Accordingly, an alternative approach to those described above has been to implant a compressible, pressure-attenuating device in the bladder in order to lower the intravesical pressure. This approach is disclosed, for example, in the following documents, all of which are incorporated herein by reference: U.S. Pat. No. 6,682,473, Matsuura et al., issued Jan. 27, 2004; U.S. Pat. No. 7,074,178, Connors et al., issued Jul. 11, 2006; and U.S. Patent Application Publication No. 2010/0222802, Gillespie, Jr. et al., published Sep. 2, 2010. According to one aspect of the foregoing approach, a compressible device is inserted, in a compacted state, into the bladder of a patient through the patient's urethra, and, then, once in the bladder, the compressible device is expanded, for example, by inflation with atmospheric air. A delivery system may be used to deliver the compressible device through the urethra and into the bladder and also may be used to expand the compressible device from its compacted state to its expanded state and to deploy the compressible device, once expanded, from the delivery system. If removal or replacement of the compressible device is desired, a removal system may be used to remove the compressible device from the bladder through the urethra.
Although the above-described implantable, compressible, pressure-attenuating device has had some success in treating urinary tract disorders, the present inventors have identified certain areas of improvement relating to the device, its introduction into a patient, its expansion and deployment within a patient, and its removal from a patient.